25 June, 2019

A Moxon for 6 meter

My new 6 m antenna is in the Norwegian ham radio magazine Amatørradio this month and the two first pages are shown below. The title is "A Moxon summer antenna for 6 meter". A very short version is here.

The antenna builds on the design of L. B. Cebik, W4RNL in QST June 2000 - "Having a Field Day with the Moxon Rectangle". That design can be found in the moxgen program which may be downloaded from AC6LA. My design frequency was 50.2 MHz - in order to cover the CW band and FT8 at 50.313 MHz.

The design with crossed glassfiber rods was inspired by that of Anthony Good, K3NG - "Homebrew Lightweight 6 Meter Moxon".

12 June, 2019

Port sharing for WSJT-X

The program for FT8 and other digital modes, WSJT-X, requires control over the communications port of a rig like the Elecraft K3. But so does the log program. Fortunately there is a solution for sharing ports. I use LP_Bridge and DXLab Commander which are both freeware.

LP_Bridge works OK, although it does abort for mysterious reasons from time to time. The setup is here:

The active ports are COM16 which connects to the radio, COM14 which connects to Commander, and COM13 which is used for the logging program.

23 May, 2019

50 MHz Doppler shift from planes

This is the first time I have observed Doppler shift in the 6 meter band. It is not so hard to see on the waterfall display of FT8.

The two stations are LA9PJA (1415 Hz) and LB6D (2477 Hz). Both of them are located in the same square as me (JO59). The other weaker signals are British and French. One can see the direct signal which has a constant frequency, and then a time-varying frequency on top of that.

16 May, 2019

Morserino now supports Single Paddle Emulation

Picture credit Morserino-32
I was happy to see the other day that the nice-looking Morserino keyer with its modern display in its latest firmware, version 1.3, now supports a new mode. It is described as follows:
A new mode in addition to Iambic A, Iambic B and Ultimatic: Non-Squeeze. This "simulates" the behavior of a single lever paddle when using a dual lever paddle. 
Operators used to single lever paddles tend to have difficulties using dual-lever paddles, as they sometimes inadvertently squeeze the paddles, especially at higher speeds. The non-squeeze mode just ignores squeezing, making it easier for these operators to use a dual lever paddle.

13 May, 2019

More spurs than I had hoped for

My Just good enough 10 MHz reference based on the direct output of a Neo-7 GPS module, described in detail before on this blog, is good in keeping long-term frequency stability. Short-term stability and phase noise is as expected not so good. When connected to the reference input of my Elecraft K3 and listening to an outdoor antenna, I get quite a substantial amount of spurs around 10 MHz radiating from the GPS module. But since the K3 itself does averaging over a second or so, this is fine from the point of view of keeping accurate frequency.

02 May, 2019

Book rather than Blog

My blog has suffered in recent years and here is the reason. For three years now I have been writing a book entitled "Waves with Power-Law Attenuation". It is now in Springer's catalogue under classical and continuum physics and I'm also very happy that it is published in the Acoustical Society of America Press series.

The emphasis is on models for waves that experience attenuation that follows a power-law in frequency. Topic-wise it is more about mechanical than electromagnetic waves, but analogies are drawn between the two fields as many of the models are the same. Power-law models in electromagnetics are in particular useful for waves in biological tissue, which is indeed also the case for acoustic and elastic waves.

24 April, 2019

The Ultimate WSPR Spot - part 2

Being spotted by the designer of my WSPR transmitter must be the ultimate WSPR spot! Perhaps only surpassed by being spotted by the designer of the mode himself, K1JT, Joe as I was four years ago.

It is Hans, G0UPL, of QRPLabs who is the designer of both my U3 to the left (turned off) and the U3S to the right. The latter was the active transmitter at the time of the spot below.

By the way, this is a line from VK2TPM, Peter's excellent WSPR Watch app for Ipod.

12 April, 2018

Power regulator works as polarity protection

Step-down converter based on LM2596. Note the damaged chip
Ok, now I've done the test. My QRPLabs U3S runs off a 12 Volt power supply. There are two step-down converters, one for 5 Volts for the processor and another adjustable one for the power amplifier, if one can call 0.2-0.5 Watts a power amplifier. See picture of these voltage converters in this post.

I happened to make a new cable for 12 Volts which had the polarities inverted - and puff - there was a noise and absolutely no response from the U3S. I feared that I had blown the entire circuit. As my power amplifier was turned off, only the 5 Volts supply was affected and upon inspection I found that the voltage converter had a destroyed chip.

Since since these step-down converter modules are so cheap on EBay, I had a spare. Luckily for me, the U3S worked as it should after the replacement. So the LM2596 can take a reversed polarity and sacrifices itself in order to protect the rest of the electronics. Nice!

This post first appeared on the LA3ZA Radio & Electronics blog.